This invention relates to carpets having a pile comprising nylon 66 fibers which have been coated with stainblocker and subjected to dry heatsetting conditions. More specifically, the invention relates to an improvement in conventional processes for continuously dyeing such carpet with acid dyes.
The term "fibers", when used herein, includes fibers of extreme length or indefinite length (i.e. filaments) and fibers of short length (i.e. staple).
The term "yarn", when used herein, means a continuous strand of fibers (singles yarn) or a yarn formed by twisting together two or more strands of fibers (plied yarn).
The term "dry heatsetting conditions", when used herein, means the conditions of time and temperature conventionally used to set the twist in nylon plied carpet yarn using dry heat, as opposed to steam, as the heat source. Typically, when nylon plied yarn is dry heatset using Suessen equipment, the yarn is exposed to temperatures ranging from 190.degree. C. to 205.degree. C. for a period about one minute.
The term stainblocker, when used herein, means a chemical which when applied to nylon fibers as a coating provides fibers having the ability to resist staining with Food, Drug and Cosmetics (FD&C) Red Dye No. 40, a acid dye colorant used to impart red color to foods, beverages and medicines, for example, to cherry Kool Aid.RTM..
U.S. Pat. No. 4,680,212 describes nylon fibers coated with stainblocker. The stainblocker coating on the fibers somewhat reduces the rate at which yarns comprising these fibers take up acid dyes. Subjecting nylon fibers to dry heatsetting conditions also reduces the rate at which the fibers take up acid dye by rendering the fibers less porous. Consequently, carpets which have nylon pile fibers that have been both coated with stainblocker and subjected to dry heatsetting conditions cannot be dyed with acid dyes to deep shades of color using conventional processes for continuously dyeing nylon carpet. In such processes a length of carpet of a selected width is longitudinally passed through a zone in which the pile fibers are treated with an aqueous liquor comprising an acid dye and then passed through an atmosphere of steam to set the dye on the fibers. The carpet is thereafter washed with water to remove excess liquor (including dye) from the fibers and, finally, dried and collected. Under these conditions, the fibers simply do not take up sufficient dye to provided deep shades of color.